﻿/*******************************************************************************************
 * Copyright (c) 2006-2009 Alex Robson, Rob Simmons, Craig Israel, and Rachel Twyford
 *
 * Use of this software in any form requires that you have both 
 * read and agreed to the following terms:
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the "Software"), 
 * to deal in the Software without restriction, including without limitation 
 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions: 
 *
 * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * Redistributions in binary form must reproduce the above copyright notice, 
 * this list of conditions and the following disclaimer in the 
 * documentation and/or other materials provided with the distribution.
 * Neither the name of Nvigorate nor the names of its contributors may 
 * be used to endorse or promote products derived from this software without 
 * specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
 * DISCLAIMED. IN NO EVENT SHALL ANY CONTRIBUTOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * ****************************************************************************************/

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using Nvigorate.Logging;

namespace Nvigorate.Relational.Mapping.Index
{
    public class MapIndexFactory
    {
        #region Fields

        private readonly MapConfigurationSection _section;
        private static volatile IMapIndex _mapIndex;
        private readonly IEnumerable<IMapLoader> _mapLoaders;

        #endregion

        #region Constructors

        public MapIndexFactory()
            : this((MapConfigurationSection)ConfigurationManager.GetSection("MapConfiguration"))
        {
        }

        internal MapIndexFactory(MapConfigurationSection configurationSection)
        {
            _section = configurationSection;
            _mapLoaders = GetMapLoadersFromConfiguration();
            ValidateConfiguration();
        }

        internal MapIndexFactory(IEnumerable<IMapLoader> mapLoaders)
        {
            _mapLoaders = mapLoaders;
        }

        #endregion

        #region Private Properties

        private string CachePath
        {
            get { return Path.Combine(_section.CacheDirectory, "mapindex.cache"); }
        }

        private Type BindingMapType
        {
            get { return typeof (BindingMap); }
        }

        #endregion

        #region Public Methods

        public IMapIndex CreateMapIndex()
        {
            Trace.TraceInformation("MapIndex began loading at {0}", DateTime.Now.ToLongTimeString());

            if (_mapIndex == null)
            {
                lock (typeof (MapIndexFactory))
                {
                    if (_mapIndex == null)
                    {
                        _mapIndex = LoadMapIndex();
                    }
                }
            }
            return _mapIndex;
        }

        public void ResetMapIndex()
        {
            lock(typeof(MapIndexFactory))
            {
                _mapIndex = null;
            }
        }
        #endregion

        #region Protected Methods

        protected virtual IMapIndex LoadMapIndex()
        {
            IMapIndex mapIndex = LoadFromCache();
            if (mapIndex == null)
            {
                mapIndex = new MapIndex();

                foreach (var loader in _mapLoaders)
                {
                    mapIndex.AddBindingMaps(loader.GetMaps());
                }

                WriteToCache(mapIndex);
            }

            return mapIndex;
        }

        #endregion

        #region Private Methods

        protected IEnumerable<IMapLoader> GetMapLoadersFromConfiguration()
        {
            var mapLoaders = new List<IMapLoader>();

            if (_section != null)
            {
                if (_section.BindingElements != null && _section.BindingElements.Count > 0)
                {
                    mapLoaders.Add(new MapElementMapLoader(_section.BindingElements.Cast<MapElement>(),
                                                           BindingMapType));
                }

                if (_section.MapScanCollection != null && _section.MapScanCollection.Count > 0)
                {
                    mapLoaders.Add(new ScanTargetMapLoader(_section.MapScanCollection.Cast<ScanTarget>(),
                                                           BindingMapType));
                }
            }

            return mapLoaders;
        }

        private void ValidateConfiguration()
        {
            if (_section.BindingElements.Count == 0 &&
                _section.RelationalElements.Count == 0 &&
                _section.MapScanCollection.Count == 0)
                LogManager.LogError(
                    new MapIndexException("There were no maps loaded during MapIndex initialization."),
                    Severities.Low);
        }

        private void WriteToCache(IMapIndex mapIndex)
        {
            if (_section == null || !_section.CachingEnabled) return;

            var formatter = new BinaryFormatter();

            using (Stream fileStream = new FileStream(CachePath, FileMode.Create))
            {
                formatter.Serialize(fileStream, mapIndex);
                fileStream.Flush();
            }
        }

        private IMapIndex LoadFromCache()
        {
            if (_section != null && _section.CachingEnabled && File.Exists(CachePath))
            {
                DateTime cacheCreatedOn = File.GetCreationTime(CachePath);
                if (DateTime.Now.Subtract(cacheCreatedOn).Hours < _section.Expiration)
                {
                    var formatter = new BinaryFormatter();
                    using (Stream fileStream = new FileStream(CachePath, FileMode.Open))
                    {
                        return (IMapIndex) formatter.Deserialize(fileStream);
                    }
                }
            }
            return null;
        }

        #endregion
    }
}